In an optical communication field, an optical waveguide substrate having an optical waveguide coupled to an optical fiber is used to make signal light incident to an optical transmission medium such as an optical fiber or the like or take out signal light propagating through the optical transmission medium. For example, an optical waveguide coupler described in Japanese Published Unexamined Patent Application No. 10-293219 has an optical waveguide on a quartz type substrate, filters or reflecting mirrors are embedded in plural dicing grooves formed in the optical waveguide, and photodetecting elements or light emitting elements adhesively attached onto the grooves.
However, the optical waveguide coupler disclosed in Japanese Published Unexamined Patent Application No. 10-293219 has the following problem. That is, in the optical waveguide coupler, when light guided along the optical waveguide is detected by the photodetecting element, the light is detected via a quartz type substrate (clad) around the optical waveguide. Or, when light from a light emitting element is made incident into the optical waveguide, it is made incident via the quartz type substrate (clad) around the optical waveguide. Accordingly, light is scattered by the quartz type substrate (clad) around the optical waveguide, and thus the optical coupling efficiency (that is, the light take-out efficiency or incident efficiency) between each of the light emitting element and the photodetecting element and the optical waveguide is lowered.
The present invention has been implemented in view of the foregoing problem, and has an object to provide an optical device that can enhance the optical coupling efficiency between a semiconductor optical element such as the light emitting element or the photodetecting element and the optical waveguide.